Difference Between Epoxy and Resin - Beginners Should Know

Have you heard of resin and epoxy, but always thought they were totally different materials? You may have also regarded them as interchangeable terms. In either case, you would be mostly correct, but also somewhat incorrect. So is epoxy and resin the same thing, or is there a notable disparity? If your curiosity brought you here, let us compare epoxy vs. resin.

Types Of Resin

Before diving into how epoxy and resin differ, let's take a brief look at the types of resin used.

  • Polyurethane Resin: This type of resin hardens very quickly so that it leaves the user only a few minutes to sufficiently mix it and pour it before it starts to solidify. This resin is also not ideal for utilization in humid climates as it is very sensitive to moisture. Also, be careful in using color additives along with this type of resin as only a select few are compatible. Their usage is also one that more than other resin types calls for protective gear and environments like safety gloves, respirator masks, and an optimally ventilated area.
  • Polyester Resin: This type of resin cures hard, so the finished product can be buffed and sanded to achieve a clear, shiny surface, but you need to know the precise amount of hardener to add in order to make it viable for use. While it is great for crafts, there is no avoiding the mess it makes or the stink that it produces. If the polished surface gets scratched, repolishing it is not a concern as it can be easily refinished. Pieces produced can be bonded with other polyester pieces to increase the overall size. One of the problems with this type of resin is that over time it will begin to yellow due to UV lighting exposure. Its composure is also more fragile, in the sense that if it is dropped, it will likely break apart. This type of resin also requires safety measures when worked with.
  • Epoxy: Widely considered an all-purpose resin type and is widely available. However, the more clear the intended design, the more expensive the cost grows. Epoxy cannot be buffed, and typically needs a supplemental finishing layer or a resin-specific sealer spray to achieve a glossy finish.

The Differences Between Resin And Epoxy

While both resin and epoxy are resin types, they have a somewhat different makeup and are therefore best used for different things. There are various types of resin including polyester, polyurethane, epoxy, and epoxy acrylates. Some of them are mixes of resin with other elements forming particular compounds, while others are synthetic variants.

Another important difference is what these different resin types, including epoxy, are used for. Commonly, when using resin in projects of various nature, one must carefully choose between Casting resin, which is better suited for moldings, jewelry, and figurines, while Epoxy Coating resin is generally used in coating surface applications.

Most of the remaining differences refer to the attributes of the particular resin type. Here are a few categories:

  • Maximum Pouring Depth: Epoxy coating resins are only recommended to be poured to a maximum of 1/4 to 1/8th inches per application as exceeding these depths causes accelerated curing. Casting resins, however, allow for more depth than that (up to several inches).
  • Viscosity: Because casting resins have a slower curing rate, they generate less heat permitting thicker layers to be poured. Its thickness, however, becomes problematic when it is attempted to be used for coating applications, as the thicker material begins to run off the sides, necessitating a frame around the project to contain any spillovers.
  • Hardness: Epoxy Coating resin is generally harder than casting resin. Casting resins permit more hardness variance through mixing ratios with other materials and the type of resin it is, including various hardener agents in varying proportions based on need.
  • Curing Time: Epoxy coating resin has a much faster curing time than casting resin. The former can cure in 12 to 24 hours, while the latter takes 24 to 48. Casting resins are thicker when dispersed, so the heat releases are significantly slowed. Therefore, pouring an epoxy too fast will likely cause the epoxy to crack, ruining your project.
  • Processing Time: Unlike curing time, processing time refers to how long it takes the material to take on a gel-like substance of “set.” When the materials are poured, bubbling is a common challenge encountered, but those can be popped before the material sets, though it's far more difficult to do so after.
  • Mixing Ratios: Casting resin offers more mixing ratio variance, while epoxy coating resin is usually 1:1. Casting resins allow for 3:1, 2:1, and 1:1 mixing ratios, which makes project work a lot easier if one is working with multiple containers with various ratios. For successful projects, the resin mixtures must be measured accurately, as failure to do so will result in the failure of resin or epoxy resin to cure.
  • UV Rays Effects: While both epoxy resin and casting resin can contain UV inhibitors when resin projects are exposed to ultraviolet rays (such as in projects used outside) its thickness promotes a more prominent yellowing effect than epoxy. This same effect varies based on the epoxy resin. In fact, none of the resins are recommended to be used in settings where they will experience prolonged UV exposure.
  • Bubbling: When casting resin is poured into molds for projects, there is a greater chance of it bubbling when embedded items are in play. The bubbling can be greatly reduced, however, by pouring resin in thin layers and treating the material with a thin coat before applying additional ones, especially if the material in question is porous.
  • Mixture Type: Epoxy resin mix with a syrupy consistency, while casting resin mixes more along the lines of a pure liquid, such as water.

Utilization of Resin Vs. Epoxy

Primarily, resin and epoxy resins are the two umbrella categories. One is a doming epoxy resin that mixes with enough viscosity to allow your project to achieve a smooth, even surface. Its propensity to finish evenly makes it an ideal resin for coating such things as furniture tops. Specifically, this type of epoxy resin is best used on projects that do not have sides. As an example, when producing a piece of art, the doming epoxy will produce a glossy shine on the surface.

The other, thinner resin is known as the casting resin, and rather than used to finish or smooth surfaces out, it is meant for pouring into containers suitable for holding resin. If your project involves a mold, especially with small, intricate nooks and grooves, the casting resin can easily penetrate these small spaces. You are essentially crafting a cast of the shape the resin is being poured into. Though this resin does have a bubbling tendency, these are easy to dispose of, as long as it is before the resin dries. Therefore, if the project involves making small or medium-sized jewelry with lots of intricate designs based on a particular mold, the casting resin is the obvious choice.

The Scientific Part

Once the resin is combined with another agent, it is no longer considered natural. Its chemical composition has been altered, and it is therefore synthetic. The chemical reaction radiates heat and releases it. But heat is released slower in casting resins, causing them to take longer to cure than epoxy resins due to the production and release of heat being lower.

Because it takes longer to harden, more of it can be poured. Since resin needs to be poured slowly, if one was to use epoxy resin for casting, it would start hardening too early, not penetrating the grooves and nooks of the mold sufficiently before doing so, producing poor or subpar results.

Of course, not all resins are the same in the curing regard, much of their hardening speed having to do with the mixing ratio and the particular resin instructions. This is not an area where eyeballing and winging it would be advised. Improperly following manufacturer directions for resin will likely end up producing undesired results, ruining the projects, as well as wasting money and time.

Some people feel that they are limited on time or constrained by impatience when operating with resin projects, so they rush. The heat produced from a rushed application is not just detrimental to the project, but can also result in burns. The resin itself will be wasted, being rendered ugly and unusable for other purposes. It is also possible that it releases harmful vapors with the rapidly exuded heat. Needless to say, when working with resin the handling party must wear both a protective breathing apparatus, such as a mask, as well as clothing suitable for bodily protection.

Working With Resin

The first part is similar to nearly any other project: preparation. Everything one may need when engaged with a project involving resin should be prepared ahead of time and laid out within reach. Because spilled over resin can harden on undesired work surfaces, it is a good idea to cover the workspace with either cardboard or disposable foil. The workspace itself should be spacious and well ventilated for the reasons noted earlier.

Any surfaces with excessive yet miniature pores should be treated first to mask the holes to prevent unwanted resin deposits from making surprise appearances from any of the small spaces. Additionally, the surfaces of wooden projects should be treated with light later of epoxy resin to produce a more sightly transition and reduce bubbling protrusions. Every resin type will have very particular manufacturer instructions, detailing the exact mixing ratio and safety notes about the resin’s use.

When you have the exact mixing proportions set of the casting resin and the hardener according to the manufacturer’s specs, you will want to begin the mixture of the two slowly and carefully. If you want your resin product to have color, this is also the time to add in any pigmentations or colored pastes. Conduct a couple of stirring sessions, but do so patiently, and break in the middle to allow the bubbles to rise and dissipate on their own.

Then carefully and gradually pour the finished mixture into your project (recess, casting mold, etc.) in your workspace. Allow the bubbles to rise as the mixture heats. You should help it along with a Bunsen burner or a hot-air dryer.


The beauty achieved from proper utilization of resin in various projects is hard to rival. It's not surprising that it has been so popular for so long. The results of resin work are atypical, however. That is to say that even when following instructions precisely it is often easy to mess it up. Even when successful, there is no long-term guarantee of no yellowing due to resin’s exposure to the elements like moisture and ultraviolet rays.

But you can certainly succeed and achieve some terrific results. There is a lot more to learn about resin, but we hope you now better understand the difference between resin and epoxy, as well as how they are related.

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1 comment

Misinformation alert! Many casting resins take far less time to cure than this article suggests! On average, I’ve found epoxy actually takes longer than resins, at 24-48 hours, whereas many resins for casting from molds can take as little as 10-60 minutes to cure! Check out smooth-ons smooth-cast line for more info! There’s are dozens and dozens of types of casting resin as numerous price points, far more variety than epoxy currently the market.

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